DI and the Cambrian Explosion

Joe Carter and PZ Myers have been having a little exchange over some claims in the new paper by Stephen Meyer of the Discovery Institute, a paper that has prompted quite a bit of discussion. I jumped into that discussion briefly in a comment on Joe's page and I'm posting this as a follow up to that discussion and Joe's response to me. A little background is needed. PZ had pointed out that Meyer had cited a couple of papers in his article that reached quite a different conclusion concerning the Cambrian explosion than the DI has been pushing. Joe had responded:

"It's saying something entirely different from what the Discovery Institute wants you to think of evolution and the Cambrian." What does the DI want us to think? PZ doesn't say.

This was the point that I jumped in and said the following:

DI has made it pretty clear what they want you to think - they want you to think that at the beginning of the Cambrian there is the sudden appearance of all the phyla on earth, with absolutely no predecessors. But the Grotzinger article, which Meyers cites as evidence for that conclusion, says quite the opposite. It says that the notion that the line between the cambrian and precambrian is the dividing line between simple and complex life and the site of a sudden explosion of complex life is no longer supported by the data. It further says that eukaryotic life was not only present in the precambrian, it was already showing diversification and complexification long before the cambrian line, and that there was a sizable adaptive radiation going on prior to the Cambrian, culminating in the "explosion". In other words, the beginning of complex life has to be pushed back considerably further than the beginning of the cambrian, which diminishes both the suddenness and the notion of an "explosion". Obviously, the DI wants the explosion to be as short and sudden as possible. They have consistently played up, rhetorically, the notion that all modern phyla were present in the cambrian, despite the fact that the phylum chordata in the cambrian amounts to a single disputed classification of an tiny organism called pikaia. Lay readers who don't know what a phylum is will be led to think that there were reptiles and mammals and amphibians and such in the cambrian, but that is obviously false.

To which Joe responded with this sneering reply:

It might be easier to take you guys from PT seriously if you actually bothered to read the work of the people you criticize. Here's an article on the Cambrian explosion that is from the Discovery Institutes website that was written by Meyers:

Cambrian rocks display about half (or more) of the basic body plans or architectural designs of the animal kingdom. Representatives of nineteen of the forty known animal phyla definitely make their first appearance in the fossil record during the Cambrian explosion. Three phyla appear in the Precambrian. Six animal phyla first appear in the fossil record after the Cambrian period, twelve more are not presented in the fossil record.

Joe, if we can be accused of anything, it is paying too much attention to what the DI crowd says, both on this issue and many others. But what happens when you read their work and hear their words constantly is that you become aware of the rhetorical strategies that they use (and remember, this is a movement born entirely out of a rhetorical strategy, outlined by Phil Johnson in many different places). On the subject of the Cambrian explosion, the consistent DI position has been to claim precisely what I said they claimed - that all the major animal groups appear "suddenly" at the beginning of the Cambrian, with the implication to the layman being that all the things we think of as animals are found in that era. In point of fact, that is nonsense. There are no insects, no amphibians or reptiles or mammals or birds or even fish that resemble anything like modern fish. Let me give you a few examples of DI fellows and their colleagues saying exactly what I said they have said:

Jonathan Wells in the Detroit News, March 14, 1999:

"...all the major types of animals appeared abruptly about 530 million years ago, in a geological period known as the Cambrian."

Paul Chien, in an interview:

A simple way of putting it is that currently we have about 38 phyla of different groups of animals, but the total number of phyla discovered during that period of time (including those in China, Canada, and elsewhere) adds up to over 50 phyla. That means [there are] more phyla in the very, very beginning, where we found the first fossils [of animal life], than exist now.

Since the Cambrian period, we have only die-off and no new groups coming about, ever.

Phil Johnson, in one of his Wedge Update reports:

The Cambrian explosion is the sudden and mysterious appearance of the basic animal groups within a very brief period of geological time around 550 million years ago. It is a phenomenon that has always been a major embarrassment to Darwinists. (Textbooks often omit to mention it for that reason.) The people who need to explain this phenomenon away (as an artifact of the fossil record) are the Darwinists, and for that very reason they would be very glad if the "explosion" could be replaced by a gradual increase in animal diversity.

And yet, Meyer cites articles that show exactly what Johnson admits would support the evolutionary perspective as support for ID's perspective.

Ray Bohlin:

All the known phyla, except one, along with the oddities with which I began this discussion, first appear in the Cambrian period. There are no ancestors. There are no intermediates. Fossil experts used to think that the Cambrian lasted 75 million years. But even that seemed to be a pretty short time for all this evolutionary change. Eventually the Cambrian was shortened to only 30 million years. And if that wasn't bad enough, the time frame of the real work of bringing all these different creatures into existence was limited to the first five to ten million years of the Cambrian.

Jonathan Wells again, from his Icons of Evolution website:

The geological period known as the Cambrian is marked by the rather sudden appearance of all the basic forms of animals now in existence.

Indeed, the DI put out a series of bookmarks based upon his Icons of Evolution book. Those bookmarks had 10 questions they encouraged students to ask their teachers, and included this question:

Why don't textbooks discuss the "Cambrian explosion," in which all major animal groups appear together in the fossil record fully formed instead of branching from a common ancestor -- thus contradicting the evolutionary tree of life?

Meyer himself, testifying before the US Civil Rights Commission:

"...the fossils of the "Cambrian explosion" which show all the basic forms of animal life appearing suddenly without clear precursors..."

I think that's enough, though I could keep going with similar quotes for hours. What I said remains true - the DI wants you to believe that all of the major animal groups appeared "suddenly" at the beginning of the Cambrian, with no new types of animals being produced since then. But what they want you to believe is false. There are in fact many forms of complex life that appeared in the Precambrian, and the appearance of most of the "major forms of animals" on earth did not occur until hundreds of millions of years later.

I think it also should be pointed out that ID has no model to explain anything about the Cambrian explosion. They only seek to poke holes in the evolutionary explanation so they can make a god of the gaps argument - "if evolution can't explain it, God must have done it". They purposely point to areas where there is a current lack of evidence so they can say, "evolutionists don't know what happened here." But at least evolutionary scientists have a model from which they can derive testable hypotheses, and into which they can fit the evidence. When looking for fossil evidence of ancestral relationships, they at least have a framework into which they can fit the evidence (or have it not fit, in which case the framework will have to be adjusted or thrown out). The truth is that we may never have a really good data set in terms of precambrian fossils. The older a fossil-bearing strata is, the less likely it has avoided deformation and metamorphosis over the eons. We currently have 3 major fossil beds from the precambrian era, and we may never find another. The fact that the life forms that appear in those fossil beds is so completely distinct from modern life forms is important for evolutionary theory, but ID has absolutely no explanation for it other than "God did it that way". And that's not really an explanation at all.

By the way, I also listed in my response on Joe's page some other examples of the DI distorting the scientific literature. His only response was a false tu quoque. The fact is that the DI has been caught repeatedly distorting the work of other scientists, citing them as offering evidence against evolutionary theory or for ID when they did nothing of the sort. They are especially fond of providing bibliographic lists to school boards (who obviously won't go out and actually read the articles listed) and then having the authors of those articles get quite irate at being cited as supporting an idea their articles emphatically rejects.